1. Field of the Invention
This invention relates to power capacitors and more particularly to a system for connecting power capacitors in a parallel, serial or a serial-parallel grouping.
2. Information Disclosure Statement
The appearance of power transistors and silicon controlled rectifiers (SCR) has resulted in an evolution of the generators used for inductive heating. The supply voltages for these switching devices are usually less than 1,000 V. As a result, the voltages supplied by transistor based or SCR based inductive heating generators are less than 1,000.times.q2, or about 700 V. In practice, most of these power sources deliver voltages ranging from 250 to 700 V.
The need to use an inductor, or a reactor, to transfer the power from the generator to the load to be heated, necessitates the creation of a reactive power whose value is usually 8 to 40 times higher than the active power. Consequently, it is necessary to have capacitor banks combined with the inductor, with characteristics allowing high currents to be supplied at voltage levels less than 700 V. The operating frequencies of these devices are usually in the range of 40 to 400 kHz.
One of the classical means to form such banks consists in mounting in parallel capacitors with the highest possible capacitance and capable of delivering currents of a few ten to a few hundred amperes. Unfortunately, the assembling of a high number of elements presents several technical problems.
The large magnetic fields produced by each capacitor in the bank may cause the heating by induction of the capacitors located close to the bank output terminals. The use of capacitors with high capacitance values may produce resonance possibilities between two or several capacitors in the bank. This phenomenon, when occurring, will destroy the bank elements.
The capacitors in the bank are usually arranged between two copper plates cooled by water circulation. As a consequence, the whole bank or the greatest part of it will have to be disassembled to replace a capacitor.
The parallel mounting of a large number of capacitors results in the creation of a high current that must be conveyed to the bank output terminals through connecting means designed to generate a negligible ohmic and inductive voltage drop. These conditions are difficult to achieve.
Therefore, it is an object of the present invention to provide an improved power capacitor bank switching device which overcomes the aforementioned problems of the prior art and provides a significant contribution to the power capacitor art.
Another object of this invention is to provide an improved power capacitor bank switching device that enables a plurality of power capacitors to be connected in a parallel, serial or a serial-parallel grouping.
Another object of this invention is to provide an improved power capacitor bank switching device that enables a plurality of power capacitors to be readily reconnected in a parallel, serial or a serial-parallel grouping.
Another object of this invention is to provide an improved power capacitor bank switching device that enables a plurality of power capacitors to be connected in a parallel, serial or a serial-parallel grouping with a negligible ohmic and inductive voltage drop.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention with in the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment of the invention.